Solder balls and conductive wires for a semiconductor package, and an improved manufacturing method, and evaporation method therefor

ABSTRACT

The surface of a solder ball and a conductive wire for a semiconductor package are coated with a predetermined colorant. Various colorants may be used according to the diameter and metal composition of the solder ball and the conductive wire. The colorant is formed by mixing organic compound and dye of a predetermined color. Examples of organic compounds excellent in physicochemical bonding with metal include benzotriazole, alkylimidazole and benzimidazole. The solder ball is fabricated by coating an organic compound of a predetermined color on the surface of a typical solder ball. The conductive wire is fabricated by coating an organic compound of a predetermined color on a general conductive wire between heat process and winding. Moreover, the solder ball is evaporated in a reflowing step after bumped via flux and the conductive wire is evaporated in a wire bonding step so that the solder ball and the conductive wire return to their unique colors.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates to semiconductor packages, and, morespecifically, to solder balls and conductive wires for a semiconductorpackage, and an improved manufacturing method and evaporation methodtherefor.

[0003] 2. Description of the Related Art

[0004] In general, solder balls for semiconductor packages are made ofan alloy containing Sn, Pb, Ag and the like. Solder balls are widelyused as input/output terminals for connecting the semiconductor packageto external devices. Since the solder balls are readily fabricated andprocessed, their melting points are relatively low. In particular,solder balls are mainly in the form of input/output terminals arrayed onone side of the semiconductor package such as BGA, PBGA and so on.

[0005] Such solder balls can have various sizes and metal componentsaccording to the size, use and type of semiconductor packages and thetaste of the customers. As recent regulations have been intensifiedagainst environmental pollution, lead-free solder balls made of only Snalso have become developed and commercialized.

[0006] The solder balls used in a semiconductor package are diverse intheir types (size and metallic composition). In general, one fabricationprocess frequently uses several types of solder balls.

[0007] For example, because one ball bumping apparatus uses severalkinds of semiconductor packages and several types of solder balls,management of the solder balls is more difficult. Management might bemore or less easy if various types of solder balls could be managed bytheir respective ball bumping apparatuses. However, since the ballbumping apparatuses are restricted in number owing to their high price,only a few ball bumping apparatuses are used to perform solder bumpingfor various types of solder balls. This further increases the risk ofmixing among different solder balls.

[0008] When the solder balls of different sizes and metalliccompositions are mixed, the solder balls may not be tightly fixed viareflow process or may be fused with different diameters. This may causevarious sequential problems in that the solder balls may not beelectrically connected to external devices.

[0009] A conductive wire for a semiconductor package is generally a thinline which is made of Au, Al or Cu, and serves to connect asemiconductor die and a substrate (e.g., a lead frame, a printed circuitboard, a circuit film, a circuit tape and so on). That is, the thinconductive wire is one of the structural materials of the semiconductorpackage, which electrically connects between the semiconductor die andthe substrate for supporting the semiconductor die.

[0010] The diameter, metal, and composition of the conductive wire canbe diversified according to the type and physical/mechanicalcharacteristic of semiconductor packages or the taste of customers. Inrecent days, copper wires have been developed and commercialized thatare more excellent in physical/electrical performance.

[0011] During the manufacturing process, a label is attached on a spoolcontainer in order to identify the conductive wire contained in thecontainer. However, since the conductive wire is taken out of thecontainer during wire bonding of the semiconductor package, it isdifficult to thereafter identify the type or diameter of the conductivewire. As the conductive wires used in semiconductor packages arerecently diversified in their types (diameter and metal), it is moredifficult to discriminate a specific conductive wire from others ifvarious types of conductive wires are used in the same fabricationprocess.

[0012] For example, one wire bonding apparatus uses several kinds ofsemiconductor packages and several types of conductive wires. Managementof the conductive wires becomes more difficult because of the differenttypes of wire that is used. Management might be more or less easy ifvarious types of conductive wires could be managed by their respectivewire bonding apparatuses. However, since the wire bonding apparatusesare restricted in number owing to their high price, only a few wirebonding apparatuses are used for wire bonding of various types ofconductive wires. This further increases the risk of mixing amongdifferent conductive wires.

[0013] If the conductive wires of different diameters and metals areerroneously used, many problems are created in that the conductive wiresare not tightly bonded to a semiconductor die or substrate, or in thatmechanical, chemical or electrical characteristics may not be obtainedat desired values.

[0014] Therefore a need existed to provide a semiconductor package and amethod of producing a semiconductor package that overcomes the aboveproblems.

BRIEF SUMMARY OF THE INVENTION

[0015] The surface of a solder ball and a conductive wire for asemiconductor package are coated with a predetermined colorant.Different colorants are used according to the diameter and metalcomposition of the solder ball and the conductive wire. The colorant isformed by mixing organic compound and dye of a predetermined color. Thesolder ball is fabricated by coating an organic compound of apredetermined color on the surface of a typical solder ball. Theconductive wire is fabricated by coating an organic compound of apredetermined color on a general conductive wire between heat processand winding. Moreover, the solder ball is evaporated in a reflowing stepafter bumped via flux and the conductive wire is evaporated in a wirebonding step so that the solder ball and the conductive wire return totheir unique colors.

[0016] The present invention is best understood by reference to thefollowing detailed description when read in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017]FIG. 1 shows solder balls of the present invention contained in aglass bottle and conventional solder balls contained in another glassbottle;

[0018]FIG. 2 shows solder balls of the present invention mixed withconventional solder balls;

[0019]FIG. 3A is a perspective view of solder balls of the presentinvention placed on a semiconductor package substrate before reflowprocess;

[0020]FIG. 3B is a perspective view of solder balls of the presentinvention fused to a semiconductor package substrate, which arevolitalized in color after reflow process;

[0021]FIG. 4 is a sectional view of a solder ball of the presentinvention after reflow process;

[0022]FIG. 5 is a flow chart showing one manufacturing method of solderballs of the present invention;

[0023]FIG. 6 is a flow chart showing one evaporation method of solderballs of the present invention;

[0024]FIG. 7 is a flow chart showing one manufacturing method of aconductive wire of the present invention; and

[0025]FIG. 8 is a flow chart showing one evaporation method of aconductive wire of the present invention.

[0026] Common reference numerals are used throughout the drawings anddetailed description to indicate like elements.

DETAILED DESCRIPTION OF THE INVENTION

[0027] Referring to FIG. 1, solder balls 2 of the present invention arecontained in a glass bottle, and conventional solder balls 4 arecontained in another glass bottle. Referring to FIG. 2, the conventionalsolder balls 4 are mixed into the. solder balls 2 of the presentinvention.

[0028] As shown in drawings, the solder balls 2 of the present inventionhave a substantially global outer shape, and the surface of the solderballs 2 is characteristically dyed with a predetermined color. Thesolder balls 2 are bumped on a semiconductor package substrate via fluxand then reflowed at high temperature to be used as input/outputterminals.

[0029] Although not shown in drawings, conductive wires of the presentinvention are fine conductors and their surface is characteristicallydyed with a predetermined color. Of course, the conductive wires areused to electrically interconnect a semiconductor die with a substrate.

[0030] Colorant is formed by adding a suitable color of dye or pigmentinto an organic compound which performs physicochemical bonding withmetal. Representative examples of organic compounds performingphysicochemical bonding with metal may include benzotriazole,alkylimidazole and benzimidazole, in which alkylimidazole is preferablesince it readily volatilizes at high temperature.

[0031] For reference benzotriazole, alkylimidazole and benzimidazolehave the following chemical structures:

[0032] Referring to FIG. 3A, a perspective view of solder balls of thepresent invention which are placed on a semiconductor package substratebefore reflow process is illustrated, and referring to FIG. 3B, aperspective view of the solder balls of the present invention fused to asemiconductor package substrate, which are volitalized in color afterreflow process is illustrated.

[0033] As shown in the drawings, colorant formed by mixing organiccompound with dye or pigment is completely removed owing tovolatilization at a high temperature atmosphere during the reflowprocess of the solder balls 2. That is, the solder balls 2 have apredetermined color when they are bumped on a substrate 6 via flux(before reflow process) as shown in FIG. 3A. However, colorant iscompletely removed from the surface of the solder balls 2′, as shown inFIG. 3B, when the solder balls 2′ completely adhere to the substrate 6via reflow process. Then, the solder balls 2′ return to their originalcolor.

[0034] Of course, the solder balls 2 are variously colored according totheir types such as size and metallic composition. Therefore, solderballs can be readily discriminated according to their sizes and metalliccompositions since different solder balls are differently colored. Forexample, lead-free solder balls may be colored blue so that they can bereadily discriminated from common gray solder balls made of Sn and Pb.Furthermore, the solder balls are coated with colorant before reflowprocess in order to prevent oxidation of the solder balls owing toexposure to the air.

[0035] Table 1 also reports results of a shear stress test after theconventional solder balls and the colored solder balls of the presentinvention are reflow-soldered or fused to substrates. TABLE 1 (unit:gf)Conventional Solder Ball Colored Solder Ball Mean 1880.2 1879.7 Max 23362304 Min 1595 1591 Standard 125.0 138.7 Deviation Index of 2.35 2.11Process Capability

[0036] As reported in Table 1, the conventional solder balls and thesolder balls of the present invention do not show a significantdifference in mean shear stress values. The conventional solder ballshave a mean shear stress of about 1880.2 while the solder balls of thepresent invention have a mean shear stress of about 1879.7. There isalso no significant difference in Index of Process Capability (C_(pk)).The conventional solder balls have Index of Process Capability of about2.35 while the solder balls of the present invention have Index ofProcess Capability of about 2.11. Therefore, it is understood that thecolored solder balls of the present invention can readily pass the shearstress test after reflow process.

[0037] Although not shown in the FIGS. 3A and 3B, as colorant formed bymixing organic compound with dye or pigment is completely volatilizedand removed, a predetermined area of the conductive wires of the presentinvention (for example, the entire area of the conductive wires placedon a heating block), to which high temperature is applied duringbonding, returns to its original color. Colorant is also removed fromboth of a ball-forming and bonding area for first bonding and a stitchbonding area for second bonding at a high temperature atmosphere so thatcolorant does not have any influence on the bonding force of theconductive wires to the semiconductor die and the substrate. That is,since colorant is completely removed through volatilization from thosehigh temperature areas (i.e., the bonding areas), degradation of thebonding force due to colorant will not occur in the bonding areas.

[0038] Of course, the conductive wires are differently colored accordingto their types such as diameter and metallic composition, therebyallowing the conductive wires to be readily discriminated. Colorationalso can prevent oxidation of the conductive wires due to exposure tothe air before wire bonding.

[0039] Accordingly, the colored solder balls and the colored conductivewires of the present invention could be discriminated with ease.

[0040] Referring to FIG. 4, a sectional view of a solder ball of thepresent invention after reflow process is illustrated.

[0041] As shown in the drawing, no voids are confirmatively formedwithin the solder ball 2′ of the present invention after reflow process.Even though the solder ball 2′ is colored, it is understood that thesolder ball 2′ is not inferior in its quality to a conventional solderball. In FIG. 4, the reference number 8 indicates a copper pattern, andreference number 10 indicates an interface between the copper pattern 8and the solder ball 2′.

[0042] Referring to FIG. 5, a flow chart showing one manufacturingmethod of solder balls of the present invention is illustrated.

[0043] As shown in drawing, the solder ball fabricating process of thepresent invention includes a primary solder ball fabricating step S51and a coloring step S52.

[0044] In the primary solder ball fabricating step S51, substantiallyglobal solder balls are fabricated by melting and cooling Sn and Pb orSn only.

[0045] In the coloring step S52, the substantially global solder ballsare immersed into a colorant solution, which contains organic compoundand dye mixed into organic compound, at a temperature of about 25 to 50°C. for about 1 to 5 minutes. The immersed solder balls are taken out ofthe colorant solution and then dried so that the surfaces of the solderballs are dyed with a predetermined color.

[0046] Of course, the coloring step is carried out with different colorsaccording to the type of the solder balls such as size and metalliccomposition so that the solder balls can be discriminated at first sightaccording to their types.

[0047] Moreover, colorant is formed by adding a suitable color of dye orpigment into the organic compound which performs physicochemical bondingwith metal. Representative examples of organic compounds performingphysicochemical bonding with metal may include benzotriazole,alkylimidazole and benzimidazole, in which alkylimidazole is preferablesince it readily volatilizes at high temperature.

[0048] Referring to FIG. 6, a flow chart showing one evaporation methodof solder balls of the present invention is illustrated.

[0049] As shown in drawing, the solder ball evaporating process of thepresent invention includes a solder ball coloring step S61, a solderball bumping step S62 and an evaporating step S63.

[0050] In the solder ball coloring step S61, colorant is applied to thesurface of the substantially global solder balls. That is, colorantcontaining organic compound mixed with a predetermined color of dye orpigment is coated on the surface of the solder balls. Of course,colorant is formed by adding a suitable color of dye or pigment intoorganic compound performing physicochemical bonding with metal.

[0051] In the solder ball bumping step S62, the solder balls aretemporarily fixed to a substrate via flux bumping.

[0052] Then, in the evaporation step S63, the substrate having thesolder balls bumped thereto is inputted into a furnace at a temperatureof about 150 to 260° C. and reflowed for about 30 to 60 seconds so thatcolorant is completely evaporated from the surface of the solder balls.

[0053] This evaporation step prevents colorant from obstructingelectrical connection between the solder balls and the substrate orbetween the solder balls and external devices.

[0054] Referring to FIG. 7, a flow chart showing one manufacturingmethod of a conductive wire of the present invention is illustrated.

[0055] As shown in drawing, the conductive wire fabricating process ofthe present includes a conductive wire fabricating step S71 and acoloring step S72.

[0056] In the conductive wire fabricating step S71, a predetermineddiameter of conductive wire is refined from metal such as Au, Al and Cuand drew from the refined metal.

[0057] Then, in the coloring step S72, the conductive wire is immersedinto a colorant solution containing mixture of organic compound and dyeor pigment at a temperature of about 25 to 50° C. for about 1 to 5minutes between heat process and winding process. The immersedconductive wire is pulled out of the colorant solution and dried so thatthe conductive wire is dyed with a predetermined color. Of course,colorant is formed by adding a suitable color of dye or pigment intoorganic compound which performs physicochemical bonding with metal.

[0058] Of course, the coloring step is carried out with different colorsaccording to the type of the conductive wire such as diameter andmetallic composition so that the conductive wire can be discriminated atfirst sight according to its type.

[0059] Referring to FIG. 8, a flow chart showing one evaporation methodof a conductive wire of the present invention is illustrated.

[0060] As shown in drawing, the conductive wire evaporating process ofthe present invention includes a conductive wire coloring step S81, aheat block preparing step S82, a first ball bonding step S83 and asecond stitch bonding step S84.

[0061] In the conductive wire coloring step S81, the surface of theconductive wire is applied by colorant as described above. That is,colorant containing organic compound mixed with a predetermined color ofdye or pigment is coated on the surface of the conductive wire. Ofcourse, the colorant is formed by adding a suitable color of dye orpigment into organic compound which performs physicochemical bondingwith metal.

[0062] In the heat block preparing step S82, wire bonding between asemiconductor die and a substrate is carried out on a heat block at atemperature of about 180 to 275° C. to evaporate colorant from the wire.That is, the wire is directly exposed to an atmosphere of 180 to 275° C.during the wire bonding step so that colorant is evaporated from thewhole wire.

[0063] In the first ball bonding step S83, heat of high temperature isproduced via electric energy and applied to one end of the wire for thepurpose of first ball bonding of the wire so that colorant can beevaporated from the one end of the wire. Since colorant is completelyevaporated, first ball bonding of the wire is performed to thesemiconductor die without degradation of bonding force resulting fromcolorant.

[0064] Then, in the second stitch bonding step S84, frictional heat viaa supersonic wave is applied to the other end of the wire for thepurpose of second stitch bonding of the wire so that colorant can beevaporated from the other end of the wire. Since colorant is completelyevaporated, second stitch bonding of the wire is performed to thesubstrate without degradation of bonding force owing to colorant.

[0065] This disclosure provides exemplary embodiments of the presentinvention. The scope of the present invention is not limited by theseexemplary embodiments. Numerous variations, whether explicitly providedfor by the specification or implied by the specification, such asvariations in structure, dimension, type of material and manufacturingprocess may be implemented by one of skill in the art in view of thisdisclosure.

What is claimed is:
 1. A solder ball for a semiconductor package used asan input/output terminal, which is bumped to a substrate for asemiconductor package via flux and reflowed at a high temperature,wherein a surface of the solder ball is colored by a colorant containingorganic compound and dye of a predetermined color.
 2. The solder ball ofclaim 1, wherein the organic compound is selected from a groupconsisting of: benzotriazole, alkylimidazole, benzimidazole, andcombinations thereof.
 3. The solder ball of claim 1, wherein the solderball is differently colored according to size and metal composition. 4.A conductive wire for a semiconductor package for electrically couplinga semiconductor die and a substrate, wherein a surface of the conductivewire is colored with a colorant containing organic compound and dye. 5.The conductive wire of claim 4, wherein the organic compound is selectedfrom a group consisting of: benzotriazole, alkylimidazole,benzimidazole, and combinations thereof.
 6. The conductive wire of claim4, wherein the conductive wire is differently colored according to sizeand metal composition.
 7. A method of manufacturing a solder ball for asemiconductor package, the method comprising the following steps of:preparing a global solder ball used as an input/output terminal, whichis bumped to a substrate for a semiconductor package via flux andreflowed at high temperature; and immersing the solder ball into acolorant solution containing organic compound and dye of a predeterminedcolor to dye the predetermined color to a surface of the solder ball. 8.The method of claim 7, wherein the dying step comprises immersing thesolder ball into the colorant solution at a temperature of approximately25 to 50° C. for approximately 1 to 5 minutes.
 9. A method ofevaporating a solder ball, comprising the following steps of: preparinga solder ball which is colored with a colorant containing organiccompound and a dye of a predetermined color; bumping the solder ball toa substrate for a semiconductor package via flux; and reflowing thesubstrate in a furnace at a temperature of approximately 150 to 260° C.for approximately 30 to 60 seconds to evaporate the colorant from asurface of the solder ball.
 10. A method of manufacturing a conductivewire for a semiconductor package, the method comprising the followingsteps of: preparing a conductive wire via refining and drawing forelectrical connection between a semiconductor die and a substrate; heattreating the conductive wire; immersing the conductive wire into acolorant solution, which contains organic compound and dye mixed intothe organic compound, at a temperature of approximately 25 to 50° C. forapproximately 1 to 5 minutes, and drying the conductive wire to dye asurface of the conductive wire with a predetermined color; and windingthe conductive wire.
 11. A method of evaporating a conductive wire,comprising the following steps of: preparing a conductive wire dyed witha colorant containing organic compound and dye of a predetermined color;wire bonding a semiconductor die and a substrate with the conductivewire, wherein the wire bonding step is prepared on a heat block at atemperature of approximately 180 to 275° C.; providing heat of hightemperature via electric energy to a first end of the wire for firstball bonding of the wire; and providing frictional heat via a supersonicwave to a second end of the wire for second stitch bonding of the wireto evaporate the colorant from a surface of the wire.